Monday, 5 June 2017

North South Interconnector - Worth the Money ?

Aside from the renewables aspect, the main justification for the North South interconnector is a deficit of reliable electricity generation in Northern Ireland.


Today, following the closure of old plant in the North, it is the South which is exporting its surplus electricity northwards - John Fitzgerald, economist.


Despite the signing of a local reserve services contract in 2015, the construction of the second North South Interconnector is the optimum solution available to alleviate this security of supply risk and allow the surplus of generation capacity which exists in Ireland to be counted towards security of supply in Northern Ireland - Eirgrid 2015.

Eirgrid now acknowledge that the commissioning of a new plant in Northern Ireland would help solve this problem :

In Northern Ireland, emissions legislation is causing a significant amount of plant to be restricted in its running hours, or to be decommissioned. This will lead to a deficit of supply. This situation would be alleviated by the second North-South Interconnector in 2021, or by the commissioning of new plant.

The assumption that South Ireland will have surplus generation to export to the North is now questionable due to new capacity market rules:

While we have reported a large surplus of plant in previous GCS reports, we now envisage that this surplus will be reduced if it is not required by the new Capacity Market. This is because the Capacity Market will only pay for enough generating units to meet the capacity requirement - Eirgrid 2017.

Interconnectors are fraught with all sorts of engineering and system problems. The interconnector from Northern Ireland to Scotland has suffered numerous faults and England no longer has enough surplus electricity to export to South Ireland through the undersea cable between the two countries (EWIC).  

The East-West interconnector (EWIC) connects the transmission systems of Ireland and Wales with a capacity of 500 MW in either direction. However, it is difficult to predict whether or not imports for the full 500 MW will be available at all times. Informed by the proposed I-SEM Capacity Market decision, we assume a 50% derating factor, i.e. 250 MW.

For the purposes of adequacy studies, we treat the Moyle interconnector similarly to EWIC, i.e. with a suitable capacity reliance (50% of 450 MW which gives 225 MW) to account for the uncertain availability of generation in Great Britain.

So assuming that the interconnector actually works for most of the time (granted this is less of a problem with overground land cables than it is with those placed under the sea), what happens if the exporting market does not have sufficient generation to export electricity through it ? Given the new capacity market rules and the planned data centres which will drive demand for electricity upwards in South Ireland, a new power station in Belfast would probably be the least costly and most secure solution to Northern Ireland's problems. 

Furthermore, if the new All Island capacity market will pay for surplus generation in the South to export to the North, then why not just allow the capacity market to pay for that generating plant in the North and save money on a completely new grid ?